Audi A6: Loud Ticking/Knocking Noise - Fix!

Hello, I've been experiencing a loud knocking or rather a loud clicking sound in my A6 with 120,000 km. It's coming from the right bank of cylinders, cylinders 1-3, on the right-hand side when facing the engine. It sounds somewhat like a misfire. It usually occurs during cold starts and improves as the engine warms up, but last time it was also present even with a warm engine, or it has even completely disappeared at times.
I'm stuck and can't seem to find a solution, as the remote diagnoses from Audi dealerships and the ÖAMTC (Austrian Automobile Club) haven't been very helpful. So far, the following has been checked:
- Camshafts (look like new)
- Dyn. Funding starts now.
- Idle speed control for fuel injectors.
- Error memory is empty.
- New diesel filter including preheating valve (anti-freeze valve).
- Needle lift sensor: electrical value OK - no error codes stored.

- Various combinations of oil viscosities, along with engine internal cleaning agents, valve lifter additives, and fuel injector cleaning additives, also did not provide any (at least for troubleshooting) improvement.

As I mentioned, it usually makes a clicking noise when starting cold, but it gets better when it's warm. However, there have also been times when it made a constant noise, or when it was completely gone and it was running smoothly as usual. No noticeable loss of power.

Thank you very much for the tips, tricks, and experiences.
Best regards,

The hydraulic lifters are likely defective. Even if the camshafts are in perfect condition, this noise can still occur. I repaired an Audi A4 2.5 TDI. The customer continued to drive the car despite the rattling noise, but the performance gradually decreased. When I disassembled the engine, I discovered that the hydraulic lifters had already fallen out of their guides, and the components were scattered. This prevented some of the valves from opening.

Well, a faulty hydraulic lifter should always produce the same symptoms. In my case, it's sometimes like this: sometimes it runs perfectly normally, and the next time, it sounds like it's about to fall apart.

Hey everyone, I'm driving an AKN and I'm also experiencing this rattling/clattering/nail-like noise.
"With mine, the noise is always there, whether it's cold or warm."

I replaced the camshaft and lifters about 5,000 km ago.
I only hear the clicking sound under load when in drive mode; I don't hear it again when the vehicle is idling.
Could the white noise coming from the c4 be caused by the plunger making similar sounds to a vacuum pump? Could that be the case here as well?
Can the fuel injectors be ruled out?

Best,
bastianna

bastianna wrote:

I replaced the camshaft and lifters about 5,000 km ago, so everything was completely new.

Where did those parts come from? I hope they weren't from eBay.

bastianna wrote:

The white smoke from the c4, which could be caused by the plunger making similar noises to a vacuum pump, could that also be the case here?

No, these engines don't use a piston pump.

bastianna wrote:

Can the fuel injectors be ruled out?

No.

hi TDI-GTI-4-Motion,
The parts were purchased from a specialized retailer.
If it's the injectors, what's wrong with them?

Best regards, Bastianna.

'In my case, the problem has been located and fixed. The issue was a broken hose clamp on the diesel filter (upstream of the ESP). The hose was therefore leaking and drawing in air, which caused the knocking/ticking sound... Luckily, that's all it was. I'm annoyed with the supposedly highly competent dealership; one of them was talking about a faulty ESP, camshafts, valve lifters, engine damage, etc...'